Footballs & Newton's Laws of Motion

by
WILLIAM MACHIN Sept. 11, 2017

William Machin

William Machin began work in construction at the age of 15, while still in high school. In 35 years, he's gained expertise in all phases of residential construction, retrofit and remodeling. His hobbies include horses, motorcycles, road racing and sport fishing. He studied architecture at Taft Junior College.

A rugby player jumps high to catch a football.
Photo Credit: Wavebreakmedia/iStock/Getty Images

At the instant a football is snapped into play, Sir Isaac Newton’s first law of motion has been demonstrated. During the course of that same play, his second and third laws of motion might be demonstrated more than once. According to folklore, the renowned physicist realized the law of gravity with the aid of a falling apple. Had football been played at the time, Newton might have formulated his laws of motion by observing a game.

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Centering and Passing

The first law of motion states that an object remains at rest or in uniform motion in a straight line unless compelled to change by an external force. Once a referee places the football at the line of scrimmage, it remains at rest until the offensive center delivers it to his quarterback or kicker. Barring high winds, when a quarterback throws a pass to his receiver, the football remains in a straight line unless tipped or knocked down by a defender.

Tackling and Hits

Newton’s second law of motion explains how the velocity of an object changes when it is subjected to an external force. This is demonstrated when a player uses his hands or body, which represent the external force, to catch the football. Newton’s formula for the second law, (F=M*A), is applied to determine the impact that changes the velocity of the ball by entering the combined weight and speed of the ball into the equation. It doesn’t take much in the way of algebraic calculation to realize players must have strong hands to catch a crisp short pass or a long pass descending from a high arc.

Catching a Football

The third law of motion tells us that every action is accompanied by an equal and opposite reaction. This is best demonstrated on long passes and punts where the the initial action of the football is upward to the point where it is affected by gravity. Receivers and kick return specialists have the ability to gauge the flight of a football from the quarterback’s hand or a kicker’s foot and get in position to make the catch. It might be fair to assume these players don’t make rapid calculations as they track the football through its arc, but the average football player understands Newton’s third law in layman’s terms: A football that goes up must come down.

The Bounce

Newton’s second and third law are demonstrated as a football is fumbled or descends after being kicked. The weight of the ball and the rate of downward acceleration caused by gravity are proportionate to the force when it hits the turf. However, the oblong shape and pointed ends of a football result in an unpredictable bounce that finds players scrambling for the elusive prize. The farther and faster it falls or is knocked to the turf, the greater the opposite reaction, or bounce, will be.